1. Field of the Invention
The invention relates generally to computer network topologies. More particularly, the invention pertains to link aggregation interface monitoring.
2. Description of Related Art
On a networked machine, it is possible to increase the communication bandwidth or the availability of network connectivity, by using multiple interfaces concurrently. This is known as “link aggregation.” Link aggregation technologies enable the machine deployed with multiple network interfaces, called “slaves,” to aggregate the bandwidth of multiple interfaces, or to maintain network connectivity despite interface failures. In particular, existing link aggregation technologies support two modes of operations: load balancing or active/standby mode. Load balancing mode requires the router(s)/switch(es) (connected to the networked machine) to support link aggregation technologies as well. In load balancing mode, the networked machine uses multiple network interfaces concurrently, to transmit/receive packets and thus to aggregate the bandwidth of these interfaces. Active/standby mode does not require link aggregation support on the router(s)/switch(es) connected to the networked machine. In this mode, the networked machine only uses one network interface, referred to the “active slave,” to transmit/receive packets, while the other network interfaces operate as “standby slaves” and do not transmit/receive. If the active slave fails, the networked machine switches to one of the standby slaves and uses the new active slave for transmitting and receiving packets.
It is possible for one or more links to go down or otherwise fail. A link failure may degrade or prevent communication among devices on the network. This can be a serious problem in network communication. In the past, monitoring techniques such as ARP monitoring and MII monitoring have been used to evaluate aggregated links.
In ARP monitoring ARP requests are sent to designated peers in the network and determine the health of slave interfaces based on any received ARP replies. One limitation on this technique is that it relies on the “liveness” of designated peers. Another limitation is that it may not be used in an active/standby link aggregation mode. In this mode, only one active slave is allowed to transmit and receive, and the health of standby slave interfaces (not allowed to send/receive packets) cannot be determined.
In MII monitoring, the technique monitors only the carrier state of aggregated interfaces. It does not detect interface failure when the carrier state is up but the link is down due to bad cables or other issues.